Contoured battery for implantable medical devices and method of manufacture

ABSTRACT

A battery having an electrode assembly located in a housing that efficiently utilizes the space available in many implantable medical devices is disclosed. The battery housing provides a cover and a shallow case a preferably planar, major bottom portion, an open top to receive the cover opposing the bottom portion, and a plurality of sides being radiused at intersections with each other and with the bottom to allow for the close abutting of other components located within the implantable device while also providing for efficient location of the battery within an arcuate edge of the device. The cover and the shallow case being substantially hermetically sealed by a laser weld technique and an insulator member disposed within the case to provide a barrier to incident laser radiation so that during welding radiation does not impinge upon radiation sensitive component(s) disposed within the case.

FIELD OF THE INVENTION

[0001] The present invention relates to the field of batteries forimplantable medical devices. More particularly, the present inventionrelates to volumetrically efficient batteries for implantable medicaldevices.

BACKGROUND OF THE INVENTION

[0002] Implantable medical devices are used to treat patients sufferingfrom a variety of conditions. Examples of implantable medical devicesare implantable pacemakers and implantable cardioverter-defibrillators(ICDs), which are electronic medical devices that monitor the electricalactivity of the heart and provide electrical stimulation to one or moreof the heart chambers, when necessary. For example, a pacemaker sensesan arrhythmia, i.e., a disturbance in heart rhythm, and providesappropriate electrical stimulation pulses, at a controlled rate, toselected chambers of the heart in order to correct the arrhythmia andrestore the proper heart rhythm. The types of arrhythmias that may bedetected and corrected by pacemakers include bradycardias, which areunusually slow heart rates, and certain tachycardias, which areunusually fast heart rates.

[0003] Implantable cardioverter-defibrillators (ICDs) also detectarrhythmias and provide appropriate electrical stimulation pulses toselected chambers of the heart to correct the abnormal heart rate. Incontrast to pacemakers, however, an ICD can also provide pulses that aremuch stronger and less frequent. This is because ICDs are generallydesigned to correct fibrillations, which is a rapid, unsynchronizedquivering of one or more heart chambers, and severe tachycardias, wherethe heartbeats are very fast but coordinated. To correct sucharrhythmias, an ICD delivers a low-, moderate-, or high-energy shock tothe heart.

[0004] Pacemakers and implantable defibrillator devices are preferablydesigned with shapes that are easily accepted by the patient's bodywhile minimizing patient discomfort. As a result, the corners and edgesof the devices are typically designed with generous radii to present apackage having smoothly contoured surfaces. It is also desirable tominimize the volume occupied by the devices as well as their mass tofurther limit patient discomfort. As a result, the devices continue tobecome thinner, smaller, and lighter.

[0005] In order to perform their pacing and/orcardioverting-defibrillating functions, pacemakers and ICDs must have anenergy source, e.g., at least one battery. Known high current powersources used in implantable defibrillator devices employ deep,prismatic, six-sided rectangular solid shapes in packaging of theelectrode assemblies. Examples of such deep package shapes can be foundin, e.g., U.S. Pat. No. 5,486,215 (Kelm et al.) and U.S. Pat. No.6,040,082 (Haas et. al.). While these prismatic cases have proveneffective for housing and electrically insulating the electrodeassemblies, there are volumetric inefficiencies associated with deepprismatic cases.

[0006] One volumetric problem associated with deep prismatic cases isthe excess volumetric size of the implantable medical device caused byplacing these prismatic batteries within the contoured implantablemedical device. As stated above, implantable medical devices arepreferably designed with shapes that are easily accepted by thepatient's body and which also minimize patient discomfort. Therefore,the corners and edges of the devices are typically designed withgenerous radii to present a package having smoothly contoured surfaces.When the deep prismatic battery is placed within the contouredimplantable device, the contours of these devices do not necessarilycorrespond and thus the volume occupied within the implantable devicecannot be optimally minimized to further effectuate patient comfort.

[0007] Another volumetric problem associated with deep prismatic casesis the excess volume within the headspace. In a typical implantabledevice battery the headspace houses the electrode connector tabs,feedthrough pin, insulators, and various other connection components. Intypical deep battery cases, the battery case has a prismatic top andthen descends downward with possibly curved sides to a bottom. Thuswhile deep cases could provide for slightly contoured sides it could notprovide for contours all throughout the battery case. Thus as shown inFIG. 13, the battery case would have to extend above the electrodeassembly to accommodate the electrode connector tabs, feedthrough pin,etc. This is volumetrically inefficient since all that technically needsto extend from the top of the electrode assembly is the electrodeconnector tabs and the feedthrough pin. This inefficiency is due tomanufacturing limitations, which make it difficult to create severalcurved surfaces in deep battery cases.

[0008] Although the use of curved battery cases in implantable devicesis known, they are typically found in devices requiring only low currentdischarge such as pacemakers as described in U.S. Pat. No. 5,549,985 andU.S. Pat. No. 5,500,026. However, these batteries used thin,flat-layered electrodes that do not package efficiently within curvedcases, thus contributing to volumetric inefficiencies. Batteries withcurved cases have been used in connection with the high currentbatteries required for, e.g., implantable defibrillator devices.However, as discussed above, the curvature of these battery cases islimited due to manufacturing limitations associated with deep cases.

[0009] For the foregoing reasons, there is a need for a contoured, lowprofile battery for implantable medical devices, which allows for shapeflexibility in the design of the battery to match the contours of animplantable device and fit within the available device space thusproviding for a reduction in the volume of the implantable device.

BRIEF SUMMARY OF THE INVENTION

[0010] The present invention comprises various embodiments which providesolutions to one or more problems existing in the prior art respectingefficient battery case design for implantable medical devices. Among theproblems in the prior art is the lack of a battery case design for usewith electrode assemblies that can be: (1) efficiently packaged withinan arcuate edge of the implantable device housings, (2) substantiallyreduces the amount of volume utilized within the implantable medicaldevice and (3) provides flexibility in the placement of the feedthroughpin.

[0011] Accordingly, it is an object of the invention to provide abattery having a high surface area electrode assembly housed in a casethat efficiently utilizes the space available within many implantablemedical devices.

[0012] Battery housings in embodiments of the invention may include oneor more of the following features: (a) a cover, (b) a shallow casehaving a (preferably) planar bottom portion, an open top to receive thecover; and at least two sides being radiused at intersections with thebottom, (c) a feedthrough assembly providing electrical communicationbetween at least one electrode and implantable medical device circuitry,(d) a coupling providing electrical communication between thefeedthrough assembly and the at least one electrode, (e) an insulatoradjacent to the cover providing a barrier between an electrode assemblyand the cover, (f) an insulator adjacent to the case providing a barrierbetween the electrode assembly and the case, and (g) a headspace portionextending from a portion of one of the sides.

[0013] Batteries in one or more embodiments of the present invention mayinclude one or more of the following features: (a) an electrode assemblyincluding an anode and a cathode, (b) an electrolyte, (c) a batteryhousing enclosing the electrode assembly and within which the electrodeassembly and the electrolyte are disposed, the housing comprising acover, a shallow case having a (preferably) planar bottom portion, anopen top to receive the cover; and a plurality of sides being radiusedat intersections with each other and with the bottom, (d) a headspaceregion extending from a portion of one of the plurality of sides, (e) afeedthrough assembly providing electrical communication between at leastone electrode and implantable medical device circuitry, (f) a couplingproviding electrical communication between the feedthrough assembly andthe at least one electrode, (g) an insulator adjacent to the coverproviding a barrier between an electrode assembly and the cover, (h) andan insulator adjacent to the case providing a barrier between theelectrode assembly and the case.

[0014] Implantable defibrillator devices in one or more embodiments ofthe present invention may include one or more of the following features:(a) a device housing comprising at least one arcuate edge, (b) acapacitor disposed within the device housing, (c) a battery disposedwithin the device housing and operatively connected to the capacitor,the battery comprising an electrode assembly, and an electrolyte (d) ahermetically sealed battery housing within which the electrode assemblyand the electrolyte are disposed, the housing comprising a cover, ashallow case having a (preferably) planar bottom, an open top to receivethe cover; and at least two sides being radiused at intersections withthe bottom wherein the radiused sides of the battery case nests withinone of the arcuate edges of the device housing, (e) a headspace regionextending from a portion of one side, and (f) a feedthrough assemblyproviding electrical communication between at least one electrode andimplantable medical device circuitry.

[0015] Methods of manufacturing batteries for implantable medicaldevices according to the present invention may include one or more ofthe following steps: (a) providing a shallow battery case having an openend, a base located opposite the open end, and a plurality of sidesbeing radiused at intersections with each other and the base, (b)inserting an electrode assembly into the battery case, (c) placing acover over the open end of the case, and hermetically sealing the coverto the case, and (d) placing an electrolyte inside the battery case.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is an exploded perspective view of a battery according tothe present invention;

[0017]FIG. 2 is a bottom profile of a battery case embodiment of thepresent invention;

[0018]FIG. 3 is a side profile battery case embodiment of the presentinvention;

[0019]FIG. 4 is cutaway side profile of several attachment embodimentsbetween a battery cover and a battery case;

[0020]FIG. 5 is a side elevated perspective of a battery case liner ofthe present invention;

[0021]FIG. 6 is a front profile of an electrolyte fillport embodiment ofthe present invention;

[0022]FIG. 7 is a side elevated perspective of an electrode assemblyembodiment of the present invention;

[0023]FIG. 8 is a side elevated perspective of an insulator cupembodiment of the present invention;

[0024]FIG. 9 is a top profile of a battery cover with a header assemblyof the present invention;

[0025]FIG. 10 is a side profile of a battery cover with a headerassembly of the present invention;

[0026]FIG. 11 is a front profile embodiment of a feedthrough assembly ofthe present invention;

[0027]FIG. 12 is a cutaway view of a headspace embodiment showing thefeedthrough pin connection with the coupling;

[0028]FIG. 13 is an elevational, exploded pictorial view of theheadspace in prior art implantable medical device batteries;

[0029]FIG. 14 is an elevated perspective of a headspace insulatorembodiment of the present invention;

[0030]FIG. 15 is a rear profile perspective of a headspace insulatorembodiment of the present invention;

[0031]FIG. 16 is an exploded perspective view of battery insulators andconnector; and

[0032]FIG. 17 is an elevated side profile of a battery connectorembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The following detailed description is to be read with referenceto the drawings, in which like elements in different drawings have likereference numerals. The drawings, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Skilled artisans will recognize that the examplesprovided herein have many useful alternatives that fall within the scopeof the claimed invention.

[0034] The present invention is not limited to implantable cardioverterdefibrillators and may be employed in many various types of electronicand mechanical devices for treating patient medical conditions such aspacemakers, defibrillators, neurostimulators, and therapeutic substancedelivery pumps. It is to be further understood; moreover, the presentinvention is not limited to high current batteries and may utilized forlow or medium current batteries. For purposes of illustration only,however, the present invention is below described in the context of highcurrent batteries.

[0035] As used herein, the term battery (or batteries) include a singleelectrochemical cell or cells. Batteries are volumetrically constrainedsystems in which the components in the case of the battery cannot exceedthe available volume of the battery case. Furthermore, the relativeamounts of some of the components can be important to provide thedesired amount of energy at the desired discharge rates. A discussion ofthe various considerations in designing the electrodes and the desiredvolume of electrolyte needed to accompany them in, for example, alithium/silver vanadium oxide (Li/SVO) battery is discussed in U.S. Pat.No. 5,458,997 (Crespi et al.). Generally, however, the battery mustinclude the electrodes and additional volume for the electrolyterequired to provide a functioning battery.

[0036] The present invention is particularly directed to high currentbatteries that at least with respect to ICDs are capable of chargingcapacitors with the desired amount of energy, preferably about 20 joulesor more, typically about 20 joules to about 40 joules, in the desiredamount of time, preferably about 20 seconds or less, more preferablyabout 10 seconds or less. These values can typically be attained duringthe useful life of the battery as well as when the battery is new. As aresult, the batteries must typically deliver up to about 5 amps at about1.5 to about 2.5 volts, in contrast to low rate batteries that aretypically discharged at much lower currents. Furthermore, the preferredbatteries must be able to provide these amounts of energy repeatedly,separated by about 30 seconds or less, more preferably by about 10seconds or less.

[0037] With reference to FIG. 1, a preferred battery according to thepresent invention is depicted. Battery 10 is comprised of a battery case12 (FIG. 2), electrode assembly 14, insulator cup 16, battery cover 18,coupling 20, headspace cover 22, feedthrough assembly 24, and batterycase liner 31. The battery case 12 is designed to enclose the electrodeassembly 14 and be hermetically sealed with battery cover 18.

[0038] With reference to FIGS. 2 & 3, a bottom and side profilerespectively is shown of a battery case. Battery case 12 is comprised ofbattery space 30 which houses electrode assembly 14, headspace 32,fillport 34, which allows for the input of electrolyte into battery 10,and open end 29. Battery case 12 is preferably generally arcuate inshape where sides 26 meet with top 28 of battery case 12. Thisconstruction provides a number of advantages including the ability toaccommodate the curved or arcuate ends of a preferred coiled electrodeassembly 14. As will be more fully discussed below, the arcuate sides 26can also nest within the arcuate edges of an implantable medical devicesuch as an implantable cardiac defibrillator.

[0039] Battery case 12 is preferably made of a medical grade titanium,however, it is contemplated that battery case 12 could be made of almostany type of material, such as aluminum and stainless steel, as long asthe material is compatible with the battery's chemistry in order toprevent corrosion. Further, it is contemplated that shallow battery case12 could be manufactured from most any process including but not limitedto machining, casting, stamping, milling, so-called rapid prototypingtechniques (e.g., using an SLA and the like) thermoforming, injectionmolding, vacuum molding, etc., however, case 12 is preferablymanufactured using a shallow drawing process. Headspace 32 housesinsulators and connector tabs, which transfer electrical energy fromelectrode assembly 14 to the implantable medical device circuitry andwill be discussed in more detail below. However, as shown in FIG. 2, asignificant amount of headspace is reduced from prior battery assembliessuch as the one shown in FIG. 13.

[0040] With reference again to FIG. 3, lip 27 is utilized to holdbattery cover 18 in place not allowing cover 18 to drop within batterycase 12. Further, lip 27 provides protection to electrode assembly 14during the welding process, which is preferably performed by laserwelding, however, other methods of attachment are contemplated. Forexample, resistance welding, brazing, soldering and similar techniquesmay be employed and/or adhesive materials may be used to couple thecover 18 to the case 12. Lip 27 provides a shelf or ledge designed toreduce the likelihood of, if not completely prevent, a portion ofradiation emitted from the laser beam from penetrating battery case 12and damaging radiation sensitive components therein. This would beespecially true if this shelf were not present and a gap between cover18 and case 12 were present there would exist a large risk thatelectrode assembly 14 could be damaged by a laser penetrating the gapand causing heat damage to electrode assembly 14.

[0041] With reference to FIG. 4, several cutaway side profiles ofattachment embodiments between a battery cover and a battery case areshown. In profile A, lip 27 is cut at 90° to provide even moreprotection during the welding process. While more protection istypically desired, the 90° lip 27 of profile A can be difficult tomanufacture. In profile B, lip 27 is bent outward and then preferablycover 18 is placed overtop and butt welded to case 12. In profile C, lip27 is also bent outward, however, in profile C, a crimp 25 is utilizedto help prevent a laser beam from penetrating battery case 12. Inprofile D, lip 27 is eliminated and the outer edge of cover 18 is bentover before being welded to case 12 to help prevent the laser frompenetrating case 12 during welding. In profile E, the outer edge of case12 is bent over top of cover 18 before being welded. In profile F, cover18 simple rests upon the upper edge of case 12 and then is butt weldedtogether. In profile G, the upper edge of case 12 is bent slightlyinward with cover 18 resting upon to be butt welded to case 12. Each ofthese embodiments is meant to provide protection to electrode assembly14 during the welding process, which is preferably performed by laserwelding, however, other methods of attachment are contemplated. Eachembodiment is meant to prevent the welding laser beam (represented bythe arrow in the Figure) from penetrating battery case 12 and damagingelectrode assembly 14. Further, the term welding can encompass manytypes of attachment such as resistance welding and brazing, however, allwelds are preferably laser welds. It is also contemplated that manytypes of attachment could be utilized without departing from the spiritof the invention.

[0042] As discussed above, traditional battery cases were deep caseswherein the opening to the case was perpendicular to the deepest portionof the battery. There are two major drawbacks to this traditionaldesign. First, there are manufacturing limitations to the amount ofcurvature, which can be implemented into the case. Therefore, most caseswould have a substantially prismatic case, which, as discussed above, isvery limiting when packaging the case within the implantable medicaldevice. Second, because the headspace exists at the open end of thecase, it consumes an entire side of the case. In contrast to deep cases,battery case 12 is manufactured using a shallow form process, whichallows for corners of case 12 to be radiused as well as providing forthe possibility of many varying shapes of case 12. By doing so, thevolume case 12 occupies is substantially reduced. Further, becausebattery case 12 can be manufactured with various shapes and contours, asubstantial amount of headspace room can be eliminated and thus morevolume within the implantable medical device can be reduced. Theinventors of the present invention have found a reduction in excess ofon the order of about 10%.

[0043] With reference to FIG. 5, a battery case liner used to isolatethe battery case from the electrode assembly is shown. Case liner 31 ispreferably comprised of ETFE and has a thickness of 0.013 cm. (0.004inches), however, other thicknesses and types of materials arecontemplated such as polypropylene, silicone rubber, polyurethane,fluoropolymers, and the like. Case liner 31 preferably has substantiallysimilar dimensions to battery case 12 except that case liner 31 wouldhave slightly smaller dimensions so that it can rest inside of batterycase 12. From the case liner's shape as shown in FIG. 5 and the batterycase's shape as shown in FIG. 2, it is clear to one of skill in the arthow case liner 31 would rest within battery case 12. For example, theheadspace area of case liner 31 would line up with headspace 32 ofbattery case 12 except it would be slightly smaller to accommodate forfillport 34.

[0044] With reference to FIG. 6, a front profile of the electrolytefillport is shown with a fillport ball seal and a closing button.Fillport 34 is used to route lithium hexafluoroarsenate electrolyte intobattery 10. Although lithium hexafluoroarsenate is preferably used forthe present embodiment, it is contemplated that most any chemicalelectrolyte could be used without departing from the spirit of theinvention. Fillport 34 is preferably laser welded to battery case 12 andpreferably has a hermetic seal to ensure no electrolyte leakage.However, it is contemplated that fillport 34 could be attached to case12 in any fashion, such as any suitable hermetic joint as is known tothose of skill in the art. Fillport 34 is preferably comprised oftitanium and has a diameter of 0.1117 inches at the top and 0.060 inchesat the bottom, however, it is fully contemplated that fillport 34 couldbe most any thickness or type of electrochemically compatible material.However, for the ease of manufacturing and reliability of the weld, case12 and fillport 34 are preferably made from the same material.

[0045] From the figure it is shown that fillport 34 has an opening 36 inwhich to receive an electrolyte injection device that transferselectrolyte from the device to battery 10 through conduit 38. Further,it is shown that the upper portion of fillport 34 is tapered so thatfillport 34 can rest within an opening in case 12 before fillport 34 iswelded to case 12. It is of note that the opening in case 12 forfillport 34 does not necessarily have to be located in headspace 32 andcan be located anywhere in case 12 or cover 18 without departing fromthe spirit of the invention. Once the electrolyte has been injectedwithin battery 10, fillport ball seal 35 is placed within conduit 38 tocreate a “press-fit” hermetic seal, which prevents any electrolyte fromescaping through conduit 38. Closing button 37 is then placed overaperture 33 and is welded to fillport 34. Closing button 37 ispreferably comprised of medical grade titanium and ball seal 35 ispreferably comprised of a titanium alloy of titanium aluminum andvanadium, however, other materials and alloys are contemplated as longas they are electrochemically compatible. It is further shown in thefigure that fillport 34 is tapered from the top to the bottom. Thisprovides for maximum space inside battery 10, further the taper providesa larger upper area for button 37 to be welded to, which allows forbutton 37 to be larger and thus easier to handle and weld to fillport34.

[0046] With further reference to FIG. 6, it is shown that fillport 34extends entirely from case 12 to cover 18. Since case 12 and cover 18are preferably 0.038 cm. (0.015 inches) thick, fillport 34 providessupport by extending from case 12 to cover 18 so that an indentation ordenting does not occur during the “press-fit” operation where ball seal35 is pressed within conduit 38. If fillport 34 did not extend from case12 to cover 18 there is a risk that denting could occur during the“press-fit” operation due to the thinness of case 12 and cover 18.Further, distal end 39 of fillport 34 is tapered so that electrolyte canfreely enter battery 10. The taper allows conduit 38 to be unobstructedby cover 18 and thus the injection of electrolyte occurs more easily.

[0047] Other fillport embodiments and locations are contemplated withoutdeparting from the spirit of the invention. One embodiment includes alow profile fillport (e.g., one that does not extend from the case tothe cover) that is located near the corners of case 12 and cover 18. Inthis embodiment, indentation during the “press-fit” is inhibited by thesupport provided by the sides of case 12 (or cover 18) in the corner.Further, this embodiment can be implemented in case 12 or cover 18 aslong as the low profile fillport is placed in a corner of the vesseldefined by case 12 and cover 18 of the battery 10. In another fillportembodiment, a filltube is located on case 12 or cover 18. After theelectrolyte is injected into battery 10, the filltube is crimped shutand welded. This embodiment eliminates the “press-fit” operation. Inanother embodiment, a plug or button is welded over or into an open portwhere the electrolyte is injected. This embodiment eliminates aredundant seal. In yet another embodiment, a gasket seal or epoxy isutilized to plug an open port.

[0048] With reference to FIG. 7, the details regarding construction ofelectrode assembly 14, such as connector tabs, electrode pouches, etc.,are secondary to the present invention and will be described generallybelow with a more complete discussion being found in, e.g., U.S. Pat.No. 5,458,997 (Crespi et al.). With reference to FIG. 7, electrodeassembly 14 is preferably a wound or coiled structure similar to thosedisclosed in, e.g., U.S. Pat. No. 5,486,215 (Kelm et al.) and U.S. Pat.No. 5,549,717 (Takeuchi et al.). However, electrode assembly 14 could bea folded or stacked electrode assembly structure. The composition of theelectrode assemblies can vary, although one preferred electrode assemblyincludes a wound core of lithium/CSVO. Other battery chemistries arealso anticipated, such as those described in U.S. Pat. No. 5,616,429 toKlementowski and U.S. Pat. No. 5,458,997 to Crespi et al., with thepreferred cores comprising wound electrodes. Such a design provides avolumetrically efficient battery useful in many different implantabledevices.

[0049] Electrode assembly 14 preferably includes an anode, a cathode,cathode connector tabs 40, anode connector tab 41, and a porous,electrically non-conductive separator material encapsulating either orboth of the anode and cathode. These three components are wound to formelectrode assembly 14. The anode portion of the electrode assembly cancomprise a number of different materials including an anode activematerial located on an anode conductor element. Examples of suitableanode active materials include, but are not limited to: alkali metals,materials selected from Group IA of the Periodic Table of Elements,including lithium, sodium, potassium, etc., and their alloys andintermetallic compounds including, e.g., Li—Si, Li—B, and Li—Si—B alloysand intermetallic compounds, insertion or intercalation materials suchas carbon, or tin-oxide. Examples of suitable materials for the anodeconductor element include, but are not limited to: stainless steel,nickel, titanium, or aluminum. However, in a preferred embodiment theanode is comprised of lithium with a titanium conductor.

[0050] The cathode portion of the electrode assembly preferably includesa cathode active material located on a cathode current collector thatalso conducts the flow of electrons between the cathode active materialand the cathode terminals of electrode assembly 14. Examples ofmaterials suitable for use as the cathode active material include, butare not limited to: a metal oxide, a mixed metal oxide, a metal sulfideor carbonaceous compounds, and combinations thereof. Suitable cathodeactive materials include silver vanadium oxide (SVO), copper vanadiumoxide, combination silver vanadium oxide (CSVO), manganese dioxide,titanium disulfide, copper oxide, copper sulfide, iron sulfide, irondisulfide, carbon and fluorinated carbon, and mixtures thereof,including lithiated oxides of metals such as manganese, cobalt, andnickel. However, in a preferred embodiment the cathode is comprised ofCSVO with a titanium conductor.

[0051] Preferably, the cathode active material comprises a mixed metaloxide formed by chemical addition, reaction or otherwise intimatecontact or by thermal spray coating process of various metal sulfides,metal oxides or metal oxide/elemental metal combinations. The materialsthereby produced contain metals and oxides of Groups IB, IIB, IIIB, IVB,VB, VIB, VIIB, and VIII of the Periodic Table of Elements, whichincludes noble metals and/or their oxide compounds.

[0052] The cathode active materials can be provided in a binder materialsuch as a fluoro-resin powder, preferably polytetrafluoroethylene (PTFE)powder that also includes another electrically conductive material suchas graphite powder, acetylene black powder, and carbon black powder. Insome cases, however, no binder or other conductive material is requiredfor the cathode.

[0053] The separator material should electrically insulate the anodefrom the cathode. The material is preferably wettable by the cellelectrolyte, sufficiently porous to allow the electrolyte to flowthrough the separator material, and maintain physical and chemicalintegrity within the cell during operation. Examples of suitableseparator materials include, but are not limited to:polyethylenetetrafluoroethylene, ceramics, non-woven glass, glass fibermaterial, polypropylene, and polyethylene.

[0054] As best seen in FIG. 1, an insulator cup 16 is used toelectrically isolate electrode assembly 14 from battery cover 18. Withreference to FIG. 8, an insulator cup embodiment of the presentinvention is shown. Insulator cup 16 includes slits 44, 46, and 48 toaccommodate connector tabs 40 and anode tab 41. Preferably insulator cup16 is comprised of ETFE with a thickness of 0.030 cm. (0.012 inches),however, it is contemplated that other thicknesses and materials couldbe used such as HDDE, polypropylene, polyurethane, fluoropolymers, andthe like. Insulator cup 16 performs several functions including workingin conjunction with battery case liner 31 to isolate battery case 12 andbattery cover 18 from electrode assembly 14. It also provides mechanicalstability for electrode assembly 14. In addition, it serves to hold thecoil assembly together which substantially aids in the manufacturing ofbattery 10. Since electrode assembly 14 is preferably a wound coil,insulator cup 16 also helps prevent assembly 14 from unwinding.Insulator cup 16 further provides protection for assembly 14 duringhandling and during the life of assembly 14. Finally, and mostimportantly cup 16 provides a thermal barrier between assembly 14 andcover 18 during the laser welding procedure that joins cover 18 withcase 12, which is discussed in more detail below.

[0055] As stated above in detail, case 12 and cover 18 are preferablywelded together to provide a hermetic enclosure for electrode assembly14. However, because of the battery's structure, the weld is performedwithin 1 mm of electrode assembly 14. Since, case 12 and cover 18 arefirst assembled before the welding process, a finite gap between case 12and cover 18 typically exists. However, any time there is a finite gapthere is the possibility that the laser beam utilized in the laserwelding process may penetrate battery 10 and damage electrode assembly14. Therefore, molded insulator cup 16 is preferably comprised of ETFEand further is preferably compounded or mixed with carbon black,although cup 16 may be simply coated with carbon black in lieu of theforegoing. The carbon coloring serves to make the insulator black. Theblack color serves to shield electrode assembly 14 from laser beampenetration into battery 10. Essentially cup 16 is opaque to the laserwavelength, which is approximately 1 micron. Alternatively, this thermalprotection could be accomplished with a metal ring compatible with case12 and cover 18, such as titanium, stainless steel, niobium, etc.,however, preferably cup 16 is an opaque polymer as discussed above.

[0056] With reference to FIGS. 9 and 10, a top and side profile of abattery cover with a feedthrough assembly is shown. Battery cover 18 iscomprised of an electrode assembly region 60, a headspace region 62, anda feedthrough aperture 64. Similar to battery case 12, battery cover 18is comprised of medical grade titanium to provide a strong and reliableweld creating a hermetic seal with the battery case. However, it iscontemplated that battery cover 18 could be made of any type of materialas long as the material was electrochemically compatible. Battery cover18 is designed to fit overtop the shallow opening 29 within lip 27 onthe perimeter of opening 29. Therefore battery cover 18 rests on thesmall lip, substantially flush with the top of opening 29 which providesfor substantial ease of manufacturing when battery cover 18 is laserwelded to battery case 12.

[0057] Feedthrough aperture 64 is tapered outwardly not only to allowfeedthrough assembly 24 to rest within aperture 64, but also to providean isolation buffer between glass member 72 and the weld which willattach feedthrough assembly 24 to battery cover 18. With reference toFIG. 11, an embodiment for the feedthrough assembly is shown.Feedthrough assembly 24 is comprised of feedthrough pin 70, glasssealing member 72, ferrule 74, flange 76, and retention slots 78. As isshown in the figure, ferrule 74 is tapered at a substantially equalangle as the tapers on feedthrough aperture 64 so that it may bereceived within aperture 64. This tapered portion of ferrule 74 is alsothe location where the weld to join feedthrough assembly 24 to batterycover 18 occurs. The taper of ferrule 74 not only places the weldfurther from glass member 72, but also creates more surface area inwhich to dissipate the heat from the weld. As is discussed above,feedthrough aperture 64 and assembly 24 can be located anywhere on case12 or cover 18.

[0058] Feedthrough pin 70 is preferably comprised of niobium, however,any conductive material could be utilized without departing from thespirit of the invention. Niobium is preferably chosen for its lowresistivity, its material compatibility during welding with titanium,and its coefficient of expansion when heated. As will be discussed inmore detail below, pin 70 is preferably welded to coupling 20 (FIG. 12)and to connector module 100 (FIG. 17) located outside of battery 10.Coupling 20 and contacts 114 and 116 on connector module 100 arepreferably made of niobium and titanium respectively. Niobium andtitanium are compatible metals, meaning that when they are weldedtogether a strong reliable weld is created. Pin 70 has a diameter of0.055 cm. (0.0216 inches), preferably selected for a high currentapplication. Glass sealing member 72 is comprised of CABAL-12(calcium-boro-aluminate) glass, which provides electrical isolation offeedthrough pin 70 from battery cover 18. The pin material is in partselected for its suitability in feedthrough assembly 24 for its abilityto join with glass sealing member 72, which results in a hermetic seal.

[0059] CABAL-12 is very corrosion resistant as well as being a goodinsulator. Therefore, CABAL-12 provides for good insulation between pin70 and battery cover 18 as well as being resistant to the corrosiveeffects of the electrolyte. Preferably glass member 72 provides anelectrical insulation resistance of 1000 M-ohms from pin 70 to ferrule74 at 100 VDC per Mil-STD 202F method 302. Glass member 72 is thenpreferably placed within a conduit on ferrule 74 having a diameter of0.060 inches. Preferably glass member 72 provides a hermetic seal bothwith pin 70 and ferrule 74 having a leak rate not exceeding 10⁻⁸ ATM STDcc/sec of helium per MIL-STD 202F method 112E. Ferrule 74 is preferablycomprised of medical grade titanium that is annealed according to ASTMF67. Although, preferable materials have been listed for the componentslisted above, it is contemplated that other materials could be utilized.Feedthrough pin 70, sealing member 72, and ferrule 74 are heatedtogether to allow the glass to melt and reform to seal within ferrule 74and around pin 70.

[0060] After pin 70, glass member 72, and ferrule 74 are placedtogether; the bottom of ferrule 74 is subjected to an overmoldingprocess where it is coated with polypropylene to provide electricalinsulation between pin 70 and ferrule 74. The polypropylene overmoldhelps prevent pin 70 from being bent over to touch ferrule 74 thuscreating an electrical short. The overmolding also provides mechanicalshort protection for other situations, such as pin 70 bending to bridgeto connector tabs 40 and 41. Further, the polypropylene coating limitsthe amount of electrolyte exposure to glass member 72. It iscontemplated that other insulation materials could be used as a coatingsuch as PETFE (polyethylene tetra fluoro ethylene), ETFE (ethylenetetrafluorethylene), polyurethane, polyethylene, and the like. Thepolypropylene molding is held in place by retention slots 78, which actto prevent the molding from twisting off or pulling away fromfeedthrough assembly 24. Further, during the overmolding process flange76 is created. Flange 76 provides a retention means for headspaceinsulator 22 (FIG. 14), which is discussed in more detail below.Preferably flange 76 has a thick plastic-thin plastic-thick plasticdesign, which allows for insulator 22 to be snapped onto flange 22.

[0061] In another embodiment, the overmolding is extended out over aplate with slots for cathode tabs 40. Tabs 40 are then welded to theplate, which in turn is welded to feedthrough pin 70. This embodimentprovides a relatively rigid system, which has advantages of preventinginsulators from inadvertently folding or collapsing out of place.

[0062] With reference to FIG. 12, an embodiment showing theinterconnection between a feedthrough pin and a coupling is shown. As isshown, coupling 20 is welded to cathode tabs 40 while anode tab 41 is incontact with battery cover 18. Coupling 20 is preferably comprised ofniobium with a diameter of 0.055 cm. (0.0216 inches), which iscompatible with pin 70. Coupling 20 is welded to feedthrough pin 70 toprovide an electrical connection between the cathode of electrodeassembly 14 and the implantable medical device. While for the purposesof this discussion coupling 20 is welded to cathode tabs 40 andfeedthrough pin 70, it is contemplated that an alternate method ofattachment may be utilized such as soldering, electrically conductiveglue, or an electrically conductive thermoset material and the like,without departing from the spirit of the invention. At the time of thepresent invention, however, the inventors have found that weldingprovides the most reliable connection. Coupling 20 allows for ease inmanufacturing by eliminating the need to bend tabs 40 or pin 70 to reacha coupling between them. Since coupling 20 has a “U” shape it allows formore compliance in aligning with the position of tabs 40 and pin 70.

[0063] What is further shown with reference to FIG. 12 is that theheadspace volume is substantially reduced when compared with priorimplantable medical device batteries as shown in FIG. 13 and asdiscussed above.

[0064] With respect to FIG. 14, a headspace insulator is shown.Preferably headspace insulator 22 is comprised of polypropylene,however, other insulative materials are contemplated. Headspaceinsulator 22 preferably covers coupling 20 and cathode tabs 40.Insulator 22 is designed to provide mechanical line of sight insulationand electrical protection from electrical shorts. Insulator 22 alsoprevents any materials from contacting cathode tabs 40 and coupling 20,which could compromise the battery's operation. With reference to FIG.15, which shows a rear profile view of the headspace insulation, slot 90is shown, which snaps onto flange 76 of feedthrough assembly 24. Thisconnection holds insulator 22 into place and protects cathode tabs 40and coupling 20 during handling and discharge.

[0065] With reference to FIG. 16, a battery assembly with insulators anda battery connector is shown. Upon battery 10 being mechanicallyassembled as described in detail above, a battery connector 100 isconnected to pin 70, which is described in more detail below. Connector100 is utilized to route the energy from battery 10 to the implantablemedical device. In an implantable cardioverter defibrillator the energywould be transferred to a switching system such as that described inU.S. Pat. No. 5,470,341 (Kuehn et al.). Battery insulators 104 and 106are held in place on battery 10 with two pressure sensitive acrylicadhesive strips 102. These strips are similar to double back adhesivetape, which is tacky on both sides of the tape. While pressure sensitiveacrylic is discussed for purposes of the embodiment, it is fullycontemplated that other methods of attachment for insulators 104 and 106could be utilized without departing from the spirit of the invention.

[0066] Insulators 104 and 106 are preferably comprised of athermoplastic polyimide film, however, other insulator materials arecontemplated. Insulators 104 and 106 provide electrical and mechanicalinsulation for battery 10. Since battery case 12 and cover 18 arenegatively charged, they need to be electrically isolated from the restof the implantable medical device. Further, insulators 104 and 106provide mechanical insulation by protecting battery 10 during handlingand thermal protection when the implantable device shields are weldedtogether, which is outside the scope of the present invention.

[0067] With reference to FIG. 17, a battery connector is shown.Connector 100 is comprised of a main body 110, a base 112, a positivecontact 114, and a negative contact 116. Main body 110 provides ahousing for base 112, positive contact 114, and negative contact 116 andis preferably comprised of polyetherimide, however other insulatormaterials are contemplated. Body 110 also acts as an insulator toelectrically isolate positive contact 114 from negative contact 116.Base 112, positive contact 114, and negative contact 116 are preferablycomprised of titanium, however other materials are contemplated.Connector 100 is placed over top of pin 70 in which pin 70 is receivedby an aperture in positive contact 114. Pin 70 is then preferably laserwelded to positive contact 114 as well as base 112 which is laser weldedto cover 18. What cannot be shown with reference to FIG. 17 is thatnegative contact 116 is in contact with base 112. Thus after the laserwelding is complete there exists a positive charge on contact 114 and anegative charge on contact 116. Positive contact 114 and negativecontact 116 are then ribbon bonded, as is known in the art, to theimplantable medical device's circuitry. It is of note that connector 100is the only exposed portion of battery 10 after it is received throughtriangular cut 108 as shown in FIG. 15. It is further noted that analternative embodiment would include a negative charge on contact 114and a positive charge on contact 116.

[0068] It will be appreciated that the present invention can take manyforms and embodiments. The true essence and spirit of this invention aredefined in the appended claims, and it is not intended that theembodiments of the invention presented herein (i.e., described and/orillustrated) should limit the scope thereof.

What is claimed is:
 1. An insulator for an electrochemical cell,comprising: a case having a bottom, an open top to receive an electrodeassembly, and at least one side extending from said bottom; and saidcase being opaque to a laser beam.
 2. An insulator according to claim 1,further comprising slots to receive at least one cathode tab and atleast one anode tab.
 3. An insulator according to claim 2, wherein theslots are located on the at least one side.
 4. An insulator according toclaim 1, wherein the case bottom is adjacent to a cell cover andprovides an electrical barrier between the electrode assembly and thecover.
 5. An insulator according to claim 4, wherein the electrodeassembly is up to five millimeters from a weld joint joining the coverwith a cell housing.
 6. An insulator according to claim 5, wherein thecase provides a thermal barrier between the weld joint and the electrodeassembly.
 7. An insulator according to claim 6, wherein the caseprovides a radiation barrier between the laser beam and the electrodeassembly.
 8. An insulator according to claim 1, wherein the case iscomprised of a material selected from the group consisting of HDDE,polypropylene, polyurethane, and fluoropolymers.
 9. An insulatoraccording to claim 1, wherein the case is comprised of ETFE.
 10. Aninsulator according to claim 9, wherein the case is comprised of ETFEcomprising a carbon black resin.
 11. An insulator according to claim 10,wherein the carbon resin provides the laser beam opacity.
 12. A battery,comprising: a electrode assembly including an anode and a cathode; anelectrolyte; a battery housing enclosing the electrode assembly andwithin which the electrode assembly and the electrolyte are disposed,the housing comprising a cover, a shallow case having a substantiallyplanar bottom, an open top to receive the cover; and a plurality ofsides; and an insulator having a bottom, an open top to receive theelectrode assembly, and at least one side extending from said bottom;said insulator being opaque to a laser beam.
 13. A battery according toclaim 12, further comprising slots in the insulator to receive at leastone cathode tab and at least one anode tab.
 14. A battery according toclaim 13, wherein the slots in the insulator are located on the at leastone side.
 15. A battery according to claim 12, wherein the insulatorbottom is adjacent to the cover and provides an electrical barrierbetween the electrode assembly and the cover.
 16. A battery according toclaim 15, wherein the electrode assembly is up to five millimeters froma weld joint joining the cover with the case.
 17. A battery according toclaim 16, wherein the insulator provides a thermal barrier between theweld joint and the electrode assembly.
 18. A battery according to claim17, wherein the insulator provides a radiation barrier between the laserbeam and the electrode assembly.
 19. A battery according to claim 12,wherein the insulator is comprised of a material selected from the groupconsisting of HDDE, polypropylene, polyurethane, and fluoropolymers. 20.A battery according to claim 12, wherein the insulator is comprised ofETFE.
 21. A battery according to claim 20, wherein the insulator iscomprised of ETFE comprising a carbon black resin.
 22. A batteryaccording to claim 21, wherein the carbon resin provides the laser beamopacity.
 23. A method of manufacturing a battery, comprising: providinga shallow battery case having an open end, a base located opposite theopen end, and a plurality of sides being radiused at intersections witheach other and the base; providing an insulator having a bottom, an opentop to receive the electrode assembly, and at least one side extendingfrom said bottom; said case being opaque to a laser beam; inserting anelectrode assembly into the insulator; placing a cover over the open endof the case, and hermetically sealing the cover to the case; and placingan electrolyte inside the battery housing.
 24. A method according toclaim 23 wherein the insulator is comprised of slots to receive at leastone cathode tab and at least one anode tab.
 25. A method according toclaim 24, wherein the slots in the insulator are located on the at leastone side.
 26. A method according to claim 23, wherein the insulatorbottom is adjacent to the cover and provides an electrical barrierbetween the electrode assembly and the cover.
 27. A method according toclaim 26, wherein the electrode assembly is up to 5 mm from a weld jointcreating the hermetic seal.
 28. A method according to claim 27, whereinthe insulator provides a thermal barrier between the weld joint and theelectrode assembly.
 29. A method according to claim 28, wherein theinsulator provides a radiation barrier between a laser beam and theelectrode assembly.